Protopanaxadiol

Protopanaxadiol at a Glance

Protopanaxadiol, or 20(S)-protopanaxadiol (PPD), is the dammarane triterpene aglycone at the foundation of one of the two great families of ginseng saponins. It is the bare, fully deglycosylated scaffold: strip every sugar off ginsenosides Rb1, Rb2, Rc, Rd, Rg3, Rh2 or compound K and you are left with this same molecule. Everything in the “PPD-type” class is a decorated version of it.

That makes it the anchor the whole protopanaxadiol family points back to. The molecule matters in two ways. First as structure — it defines the class, sits at the end of the gut-bacterial deglycosylation cascade that converts the poorly-absorbed parent saponins into smaller actives, and is far more lipophilic and membrane-permeable than any of the glycosides above it ^{11Reference 11Verstraeten SL et al. · 2020ReviewLipid membranes as key targets for the pharmacological actions of ginsenosides — reviewView study →}. Second as a candidate in its own right — isolated PPD has a genuine, if entirely preclinical, antidepressant and anti-stress signal in rodents, plus anticancer activity in cell and animal models ^{1,4,7Reference 1Xu C et al. · 2010AnimalXu C, Teng J, Chen W, et al. (2010). 20(S)-protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal tests — rodent, in vivo. Progress in Neuro-Psychopharmacology & Biological Psychiatry. https://pubmed.ncbi.nlm.nih.gov/20647027/View study →Reference 4Oh HA et al. · 2015AnimalAnti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivoView study →Reference 7Zhang Z et al. · 2015In vitroTRAIL pathway is associated with inhibition of colon cancer by protopanaxadiol — in vitro / animal modelView study →}.

The standard ginseng caveat governs everything below. Free PPD is largely a metabolite, not something the plant stores in quantity; and the human clinical evidence for ginseng is whole-extract, not isolated aglycone. What follows is mostly the isolated molecule in animals and cells.

The Protopanaxadiol Scaffold

This is the reason the page exists. Protopanaxadiol is not just another ginsenoside — it is the common aglycone (sapogenin) that the entire protopanaxadiol-type class is assembled on.

The dammarane backbone. PPD is a tetracyclic dammarane triterpene, formally dammar-24-ene-3β,12β,20(S)-triol — a steroid-like four-ring core carrying hydroxyls at C-3, C-12 and C-20 ^{14Reference 14Tanaka O et al. · 1966Chemical studies on the oriental plant drugsView study →}. In the intact plant saponins, sugar chains are hung off the C-3 and C-20 hydroxyls; the number, position and identity of those sugars is the only thing that distinguishes one PPD-type ginsenoside from another:

• Ginsenoside Rb1, Rb2, Rc, Rd — the abundant parent saponins, di-glycosylated at both C-3 and C-20.
• Ginsenoside Rg3, Rh2 — partially deglycosylated intermediates.
• Compound K — the mono-glucoside at C-20, the major absorbable metabolite in blood and itself markedly anti-inflammatory, active at low concentrations where its parent Rb1 is not ^{8Reference 8Wang CZ et al. · 2018AnimalAmerican ginseng microbial metabolites attenuate DSS-induced colitis and abdominal pain — mouse, in vivoView study →}.
• Protopanaxadiol — the endpoint: no sugars at all.

The deglycosylation cascade ends here. Taken by mouth, the large parent saponins are barely absorbed — their dammarane skeleton plus bulky sugars gives poor solubility and poor membrane permeability ^{10Reference 10Hu QR et al. · 2023ReviewMethods on improvements of the poor oral bioavailability of ginsenosides: pre-processing, structural modification, drug combination, and micro- or nano-delivery system — reviewView study →}. Colonic bacteria strip their sugars stepwise — for the Rb1 branch, roughly Rb1 → Rd → F2 → compound K → PPD — each step making the molecule smaller, less polar and more absorbable ^{15Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}. Protopanaxadiol is the terminal aglycone of that pathway: the most-processed, least-glycosylated form the class reduces to. This is why “ginseng pharmacology” is often really the pharmacology of these downstream metabolites, not of the saponins actually swallowed ^{15Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}.

Why the bare scaffold behaves differently. Sugars are hydrophilic anchors. Removing them progressively raises lipophilicity, and binding of PPD-type ginsenosides to lipid membranes rises inversely with the number of sugar residues — the fewer the sugars, the deeper the molecule partitions into the membrane hydrophobic core ^{11Reference 11Verstraeten SL et al. · 2020ReviewLipid membranes as key targets for the pharmacological actions of ginsenosides — reviewView study →}. The naked aglycone is therefore the most membrane-permeable member of its family, better able to cross the gut wall and cell membranes and to perturb membranes directly ^{11Reference 11Verstraeten SL et al. · 2020ReviewLipid membranes as key targets for the pharmacological actions of ginsenosides — reviewView study →}. That single physical fact — lipophilicity climbing as glycosylation falls — links the scaffold’s structure to both its absorption and much of its bioactivity.

PPD versus PPT. Ginseng saponins split into exactly two aglycone lineages. Protopanaxadiol (this molecule) carries hydroxyls at C-3, C-12 and C-20. Protopanaxatriol (PPT) — the aglycone of ginsenoside Rg1, Re and Rf — adds a fourth hydroxyl at C-6 (dammar-24-ene-3β,6α,12β,20(S)-tetrol) ^{14Reference 14Tanaka O et al. · 1966Chemical studies on the oriental plant drugsView study →}. That one extra oxygen defines the whole PPD/PPT divide, and the PPD:PPT ratio (often read as Rb1:Rg1) is the classic chemotaxonomic fingerprint separating Panax ginseng from P. quinquefolius. The two aglycones even diverge pharmacologically: in immobilised-mouse anti-stress work, PPD’s anxiolytic effect ran through GABAergic signalling while PPT’s ran through serotonergic signalling ^{4Reference 4Oh HA et al. · 2015AnimalAnti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivoView study →}.

Protopanaxadiol as a Drug Candidate

Beyond its structural role, isolated PPD has been pursued as a molecule in its own right — most seriously as an antidepressant/anxiolytic, secondarily as an anticancer isolate.

Antidepressant. The headline finding is that orally-dosed 20(S)-protopanaxadiol produced antidepressant-like activity as potent as fluoxetine across the tail-suspension test, forced-swim test and the rat olfactory-bulbectomy model, with treated animals showing higher brain monoamine levels and a mild reuptake-inhibitory effect in vitro ^{1Reference 1Xu C et al. · 2010AnimalXu C, Teng J, Chen W, et al. (2010). 20(S)-protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal tests — rodent, in vivo. Progress in Neuro-Psychopharmacology & Biological Psychiatry. https://pubmed.ncbi.nlm.nih.gov/20647027/View study →}. Later work reproduced an antidepressant-like effect in a chronic social-defeat-stress model, tied to normalised neurotransmitter and corticosterone levels and reduced oxidative stress ^{2Reference 2Jiang N et al. · 2019AnimalAntidepressant-like effects of 20(S)-protopanaxadiol in a mouse model of chronic social defeat stress and the related mechanisms — mouse, in vivoView study →}. This line is real enough that PPD’s antidepressant use was patented (Patents: not yet researched below). The honest counterweight: a head-to-head comparison of ginsenoside Rb3 against its deglycosylated derivatives found the fully-deglycosylated PPD aglycone was the weakest of the set in acute despair tests, with the partially-glycosylated Rg3/Rh2/compound K outperforming it — so “more deglycosylated” is not simply “more active” ^{3Reference 3Zhang H et al. · 2016AnimalAntidepressant-like effects of ginsenosides: a comparison of ginsenoside Rb3 and its four deglycosylated derivatives, Rg3, Rh2, compound K, and 20(S)-protopanaxadiol in mice models of despair — mouse, in vivoView study →}.

Anxiolytic / anti-stress. In immobilised mice, PPD was anxiolytic in the elevated-plus-maze at a level comparable to buspirone, an effect blocked by the GABA-receptor antagonists flumazenil and bicuculline, and it suppressed stress-induced corticosterone and IL-6 ^{4Reference 4Oh HA et al. · 2015AnimalAnti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivoView study →}. Mechanistic caution applies: on recombinant GABAA receptors PPD inhibited GABA-evoked currents (IC50 ≈ 23 µM, non-competitive) rather than potentiating them, so the receptor-level story is not a simple benzodiazepine-like action ^{5Reference 5Lee BH et al. · 2012In vitroEffects of ginsenoside metabolites on GABAA receptor-mediated ion currents — in vitro (Xenopus oocyte expression)View study →}.

Anticancer. As the lipophilic aglycone, PPD is repeatedly the more cytotoxic member of its family against tumour cells. In colon cancer it inhibited growth through the TRAIL apoptotic pathway, modulating p53 and the death receptors DR4/DR5 ^{7Reference 7Zhang Z et al. · 2015In vitroTRAIL pathway is associated with inhibition of colon cancer by protopanaxadiol — in vitro / animal modelView study →}. This is in-vitro and rodent work on the isolate, consistent with the broader pattern that deglycosylated ginseng metabolites are more anticancer-active than their parent saponins.

What It's Used For

PPD’s pharmacology is genuine but almost entirely preclinical and almost entirely on the isolate — and it is shadowed by the fact that free PPD is a metabolite, generated variably by each person’s gut flora, not a molecule people dose directly ^{15Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume, tempered for isolate-vs-plant match and the fact that PPD is a variably-generated metabolite. A beta, not a validated metric. Every row rests on the isolated molecule in animals or cells; no human isolate data exist, so scores are capped accordingly. Each application links to its write-up.

01AntidepressantShaky40%Isolated oral PPD, multiple rodent despair + chronic-stress models; potency ~fluoxetine, but weakest of a deglycosylation series in one head-to-head ^{1,2,3Reference 1Xu C et al. · 2010AnimalXu C, Teng J, Chen W, et al. (2010). 20(S)-protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal tests — rodent, in vivo. Progress in Neuro-Psychopharmacology & Biological Psychiatry. https://pubmed.ncbi.nlm.nih.gov/20647027/View study →Reference 2Jiang N et al. · 2019AnimalAntidepressant-like effects of 20(S)-protopanaxadiol in a mouse model of chronic social defeat stress and the related mechanisms — mouse, in vivoView study →Reference 3Zhang H et al. · 2016AnimalAntidepressant-like effects of ginsenosides: a comparison of ginsenoside Rb3 and its four deglycosylated derivatives, Rg3, Rh2, compound K, and 20(S)-protopanaxadiol in mice models of despair — mouse, in vivoView study →}

02Anxiolytic / anti-stressShaky34%Isolated PPD, immobilised-mouse elevated-plus-maze ~buspirone; GABAergic, ↓corticosterone/IL-6 ^{4,5Reference 4Oh HA et al. · 2015AnimalAnti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivoView study →Reference 5Lee BH et al. · 2012In vitroEffects of ginsenoside metabolites on GABAA receptor-mediated ion currents — in vitro (Xenopus oocyte expression)View study →}

03Anticancer (colorectal)Shaky30%Isolated PPD in colon-cancer cells/rodents; TRAIL/DR4-DR5/p53 apoptosis; no clinical endpoint ^{7Reference 7Zhang Z et al. · 2015In vitroTRAIL pathway is associated with inhibition of colon cancer by protopanaxadiol — in vitro / animal modelView study →}

Mechanisms

The load-bearing point is the last row: as the least-glycosylated form of its class, PPD partitions most deeply into membranes ^{11Reference 11Verstraeten SL et al. · 2020ReviewLipid membranes as key targets for the pharmacological actions of ginsenosides — reviewView study →}, which plausibly underlies both its better cell entry and its direct membrane-level effects.

Pharmacokinetics

PPD’s kinetics are the crux of the “scaffold” story. Unlike its parent saponins — large, polar molecules with very poor oral absorption (rat oral bioavailability of Rb1 around 4% or less) ^{16Reference 16Xu QF et al. · 2003AnimalPharmacokinetics and bioavailability of ginsenoside Rb1 and Rg1 from Panax notoginseng in rats — rat pharmacokineticsView study →} — the deglycosylated aglycone is comparatively lipophilic and well-absorbed across the gut wall ^{11Reference 11Verstraeten SL et al. · 2020ReviewLipid membranes as key targets for the pharmacological actions of ginsenosides — reviewView study →}. But better absorption does not translate into high systemic exposure: a systematic rat-and-dog ADME study found PPD’s oral absorption is nearly complete, yet its bioavailability stays low because most of the absorbed dose is lost to first-pass metabolism; PPD is highly plasma-protein-bound, undergoes extensive hydroxylation, and its metabolites are excreted in faeces and urine with evidence of enterohepatic circulation ^{9Reference 9Li P et al. · 2024AnimalSystematic studies on the kinetic process of 20(S)-protopanaxadiol in rats and dogs: absorption, distribution, metabolism and excretion — rat/dog pharmacokineticsView study →}. Two consequences for the compound page: (1) PPD is more absorbable than the glycosides above it but is not a high-exposure molecule in its own right; and (2) because free PPD in the body is largely made from the parent ginsenosides by gut bacteria, systemic exposure varies between individuals and depends on the microbiome, exactly as for compound K ^{15Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}.

Clinical Trials

There are no registered clinical trials of isolated protopanaxadiol. Human evidence attached to “ginseng” is at the whole-extract level and cannot be assigned to PPD specifically; the entire isolated-molecule literature is preclinical.

Last checked: July 2026.

Isolate vs. Plant Studies

PPD sits at an unusual place on the isolate-vs-plant axis, because it is both an isolate and a metabolite of the plant’s own saponins. The behavioural pharmacology — antidepressant ^{1,2Reference 1Xu C et al. · 2010AnimalXu C, Teng J, Chen W, et al. (2010). 20(S)-protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal tests — rodent, in vivo. Progress in Neuro-Psychopharmacology & Biological Psychiatry. https://pubmed.ncbi.nlm.nih.gov/20647027/View study →Reference 2Jiang N et al. · 2019AnimalAntidepressant-like effects of 20(S)-protopanaxadiol in a mouse model of chronic social defeat stress and the related mechanisms — mouse, in vivoView study →}, anxiolytic ^{4Reference 4Oh HA et al. · 2015AnimalAnti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivoView study →}, anticancer ^{7Reference 7Zhang Z et al. · 2015In vitroTRAIL pathway is associated with inhibition of colon cancer by protopanaxadiol — in vitro / animal modelView study →} — is uniformly the isolated aglycone in rodents or cells, a consistent mechanistic base but no more. The human efficacy evidence is entirely whole-ginseng extract, standardised to total ginsenosides, not to PPD. And the connective tissue between the two is the microbiome: what ginseng ultimately delivers to tissue is a mixture of downstream metabolites — compound K and PPD among them — generated in amounts that differ from person to person ^{15Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}. So PPD is neither a clean “isolate the plant contains” nor a validated drug; it is the deglycosylated endpoint that some of the swallowed saponins become, tested in isolation. The correct framing: strong isolate mechanism + meaningful clinical whole-extract evidence + no direct human isolate data — not interchangeable.

Its Role in Plants

In the plant, protopanaxadiol is a biosynthetic intermediate, not an end product. The dammarane skeleton is built by dammarenediol-II synthase (PgDDS), the first committed enzyme of ginsenoside biosynthesis, which cyclises the universal triterpene precursor 2,3-oxidosqualene to dammarenediol-II. The cytochrome P450 CYP716A47 then hydroxylates dammarenediol-II at C-12 to yield protopanaxadiol ^{12Reference 12Han JY et al. · 2011The Cyt P450 enzyme CYP716A47 catalyzes the formation of protopanaxadiol from dammarenediol-II during ginsenoside biosynthesis in Panax ginseng — plant enzymologyView study →}. PPD is the branch point of the pathway: a second P450 (CYP716A53v2) hydroxylates it at C-6 to make protopanaxatriol, while glycosyltransferases decorate the C-3 and C-20 hydroxyls to build the mature Rb-series ginsenosides. Because the plant rapidly glycosylates the aglycone into storage saponins, free protopanaxadiol is scarce in living root tissue — it exists mostly transiently in biosynthesis, and is released later by digestion or processing rather than stored as such.

Prevalence in Nature

Protopanaxadiol occurs across the Panax genus — Asian ginseng (Panax ginseng), American ginseng (P. quinquefolius) and notoginseng (P. notoginseng) — but almost always in bound (glycosylated) form, as the aglycone core of the abundant PPD-type ginsenosides rather than as the free molecule. In the raw dried root the free aglycone is present only in trace amounts; the PPD-type saponins it underlies, by contrast, are major constituents (in Korean red ginseng, ginsenoside Rb1 alone runs around 5.8 mg/g of root). Free PPD accumulates chiefly through two routes downstream of the intact plant: gut-bacterial deglycosylation of the ingested saponins ^{15Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}, and thermal/fermentation processing — steaming to make red ginseng, and microbial fermentation, both hydrolyse sugars off the parent saponins and raise the levels of deglycosylated species including PPD. So the honest statement is that this molecule’s “abundance in nature” is really the abundance of its glycosides; the free aglycone is a metabolite and a processing product, quantified far less often than its parent saponins.

Discovery & Synthesis

Protopanaxadiol was defined by the mid-twentieth-century Japanese ginseng-chemistry school. Osamu Tanaka, Masahiro Nagai and Shoji Shibata established its structure and stereochemistry in 1966, naming it the “genuine sapogenin” — the true aglycone — shared by ginsenosides Rb1, Rb2 and Rc, i.e. dammar-24-ene-3β,12β,20(S)-triol ^{14Reference 14Tanaka O et al. · 1966Chemical studies on the oriental plant drugsView study →}. The term protopanaxadiol itself encodes the discovery: the proto (“original/parent”) panaxadiol aglycone, distinguished from the artefactual “panaxadiol” that harsher acid hydrolysis had produced earlier by cyclising the C-20 side chain.

Manufacture today does not rely on extracting the trace free aglycone from root. Two routes dominate: enzymatic or acid/thermal deglycosylation of the plentiful parent saponins (steaming, fermentation, or β-glucosidase treatment to strip sugars down to PPD), and, increasingly, microbial biosynthesis — engineered Saccharomyces cerevisiae expressing PgDDS plus the CYP716A47 oxidation system produce PPD directly from simple feedstocks, with fusion-protein and P450-optimisation work raising catalytic output several-fold for scalable fermentation ^{13Reference 13Zhao F et al. · 2016Optimization of a cytochrome P450 oxidation system for enhancing protopanaxadiol production in Saccharomyces cerevisiae — metabolic engineeringView study →}. The molecule is thus best made either by taking apart the abundant saponins or by building it up in yeast — not by isolating it from the plant where it barely exists free.

Patents: not yet researched.

Toxicity & Safety

Protopanaxadiol carries a low toxicity flag, consistent with its status as a normal ginseng metabolite that humans generate whenever they consume ginseng. It is well tolerated in the rodent studies above, and its poor net systemic exposure (near-complete absorption but heavy first-pass loss) limits how much circulates from an oral dose ^{9Reference 9Li P et al. · 2024AnimalSystematic studies on the kinetic process of 20(S)-protopanaxadiol in rats and dogs: absorption, distribution, metabolism and excretion — rat/dog pharmacokineticsView study →}. The caveats are isolate-level and largely theoretical rather than drawn from ginseng use:

Safety at a Glance

✅ Low / no toxicity

• A normal, well-tolerated ginseng metabolite. PPD is generated by everyone’s gut flora from dietary ginsenosides and shows low toxicity in rodent studies at the doses used ^{1,4Reference 1Xu C et al. · 2010AnimalXu C, Teng J, Chen W, et al. (2010). 20(S)-protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal tests — rodent, in vivo. Progress in Neuro-Psychopharmacology & Biological Psychiatry. https://pubmed.ncbi.nlm.nih.gov/20647027/View study →Reference 4Oh HA et al. · 2015AnimalAnti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivoView study →}.
• Isolate ≠ ginseng. The behavioural and anticancer data are the pure aglycone in animals/cells at defined doses — they do not license taking concentrated PPD, and the potent antidepressant/anticancer signals imply real pharmacological activity that could interact with CNS or other drugs.
• Membrane-active by design. As the most lipophilic, membrane-partitioning form of its class ^{11Reference 11Verstraeten SL et al. · 2020ReviewLipid membranes as key targets for the pharmacological actions of ginsenosides — reviewView study →}, PPD perturbs membranes directly; relevance to normal tissue at physiological exposure is unquantified.
• Metabolite variability. Real-world exposure depends on the gut microbiome and on first-pass metabolism, so response to ginseng-derived PPD varies between people and is blunted by antibiotics ^{15Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}.

Dedicated human interaction, reproductive and repeat-dose toxicology for isolated PPD is not characterised; pregnancy/lactation is a per-herb/per-supplement decision made on the ginseng monograph, not on this molecule page. Absence of data here is not evidence of safety.

Dosage

There is no established human dose of isolated protopanaxadiol — it is a research compound and a metabolite, not a standardised supplement. For orientation only, the preclinical antidepressant and anxiolytic studies dosed rodents in roughly the single-digit to low-tens of mg/kg range by oral or intraperitoneal routes ^{1,4Reference 1Xu C et al. · 2010AnimalXu C, Teng J, Chen W, et al. (2010). 20(S)-protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal tests — rodent, in vivo. Progress in Neuro-Psychopharmacology & Biological Psychiatry. https://pubmed.ncbi.nlm.nih.gov/20647027/View study →Reference 4Oh HA et al. · 2015AnimalAnti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivoView study →}, figures chosen for the experiment and not convertible to a human dose. Because free PPD in the body is largely generated by gut bacteria from the parent ginsenosides and then heavily first-pass-metabolised ^{9,15Reference 9Li P et al. · 2024AnimalSystematic studies on the kinetic process of 20(S)-protopanaxadiol in rats and dogs: absorption, distribution, metabolism and excretion — rat/dog pharmacokineticsView study →Reference 15Hasegawa H · 2004ReviewProof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — reviewView study →}, an oral milligram figure of the aglycone would not map cleanly onto delivered tissue exposure in any case. In practice, human intake of PPD happens indirectly, through whole standardised ginseng extracts, where it is one downstream metabolite among many. These are doses studied in research and are not a personal recommendation.

References

1. Xu C, Teng J, Chen W, et al. (2010). 20(S)-protopanaxadiol, an active ginseng metabolite, exhibits strong antidepressant-like effects in animal tests — rodent, in vivo. Progress in Neuro-Psychopharmacology & Biological Psychiatry. https://pubmed.ncbi.nlm.nih.gov/20647027/
2. Jiang N, Lv J, Wang H, et al. (2019). Antidepressant-like effects of 20(S)-protopanaxadiol in a mouse model of chronic social defeat stress and the related mechanisms — mouse, in vivo. Phytotherapy Research. https://pubmed.ncbi.nlm.nih.gov/31353678/
3. Zhang H, Li Z, Zhou Z, et al. (2016). Antidepressant-like effects of ginsenosides: a comparison of ginsenoside Rb3 and its four deglycosylated derivatives, Rg3, Rh2, compound K, and 20(S)-protopanaxadiol in mice models of despair — mouse, in vivo. Pharmacology, Biochemistry, and Behavior. https://pubmed.ncbi.nlm.nih.gov/26528894/
4. Oh HA, Kim DE, Choi HJ, et al. (2015). Anti-stress effects of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol in immobilized mice — mouse, in vivo. Biological & Pharmaceutical Bulletin. https://pubmed.ncbi.nlm.nih.gov/25747994/
5. Lee BH, Choi SH, Hwang SH, et al. (2012). Effects of ginsenoside metabolites on GABAA receptor-mediated ion currents — in vitro (Xenopus oocyte expression). Journal of Ginseng Research. https://pubmed.ncbi.nlm.nih.gov/23717104/
6. Duan Y, Nicholson RA (2008). 20(S)-protopanaxadiol and the ginsenoside Rh2 inhibit Na+ channel-activated depolarization and Na+ channel-dependent amino acid neurotransmitter release in synaptic fractions isolated from mammalian brain — in vitro. Comparative Biochemistry and Physiology. Toxicology & Pharmacology. https://pubmed.ncbi.nlm.nih.gov/18262850/
7. Zhang Z, Du GJ, Wang CZ, et al. (2015). TRAIL pathway is associated with inhibition of colon cancer by protopanaxadiol — in vitro / animal model. Journal of Pharmacological Sciences. https://pubmed.ncbi.nlm.nih.gov/25704023/
8. Wang CZ, Yao H, Zhang CF, et al. (2018). American ginseng microbial metabolites attenuate DSS-induced colitis and abdominal pain — mouse, in vivo. International Immunopharmacology. https://pubmed.ncbi.nlm.nih.gov/30212750/
9. Li P, Zhang M, Chen M, et al. (2024). Systematic studies on the kinetic process of 20(S)-protopanaxadiol in rats and dogs: absorption, distribution, metabolism and excretion — rat/dog pharmacokinetics. Frontiers in Pharmacology. https://pubmed.ncbi.nlm.nih.gov/38966555/
10. Hu QR, Hong H, Zhang ZH, et al. (2023). Methods on improvements of the poor oral bioavailability of ginsenosides: pre-processing, structural modification, drug combination, and micro- or nano-delivery system — review. Journal of Ginseng Research. https://pubmed.ncbi.nlm.nih.gov/38107396/
11. Verstraeten SL, Lorent JH, Mingeot-Leclercq MP. (2020). Lipid membranes as key targets for the pharmacological actions of ginsenosides — review. Frontiers in Pharmacology. https://pubmed.ncbi.nlm.nih.gov/33041822/
12. Han JY, Kim HJ, Kwon YS, Choi YE. (2011). The Cyt P450 enzyme CYP716A47 catalyzes the formation of protopanaxadiol from dammarenediol-II during ginsenoside biosynthesis in Panax ginseng — plant enzymology. Plant & Cell Physiology. https://pubmed.ncbi.nlm.nih.gov/22039120/
13. Zhao F, Bai P, Liu T, et al. (2016). Optimization of a cytochrome P450 oxidation system for enhancing protopanaxadiol production in Saccharomyces cerevisiae — metabolic engineering. Biotechnology and Bioengineering. https://pubmed.ncbi.nlm.nih.gov/26757342/
14. Tanaka O, Nagai M, Shibata S. (1966). Chemical studies on the oriental plant drugs. XIV. Protopanaxadiol, a genuine sapogenin of ginseng saponins. Chemical & Pharmaceutical Bulletin. https://www.jstage.jst.go.jp/article/cpb1958/14/6/14_6_595/_article
15. Hasegawa H. (2004). Proof of the mysterious efficacy of ginseng: metabolic activation of ginsenoside — deglycosylation by intestinal bacteria and esterification with fatty acid — review. Journal of Pharmacological Sciences. https://pubmed.ncbi.nlm.nih.gov/15215638/
16. Xu QF, Fang XL, Chen DF. (2003). Pharmacokinetics and bioavailability of ginsenoside Rb1 and Rg1 from Panax notoginseng in rats — rat pharmacokinetics. Journal of Ethnopharmacology. https://pubmed.ncbi.nlm.nih.gov/12648814/

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